1. Field of the Invention
The present invention relates to the templating and placement of prosthetic intervertebral discs and, more particularly, to new and improved apparatus and methods for enabling a physician to select the optimal size of a prosthetic disc and to position it accurately between vertebrae to optimize its dynamic function.
2. Description of the Background Art
The degeneration of human intervertebral discs is increasingly being treated with prosthetic intervertebral discs. The critical parameters for a successful surgical outcome are appropriate templating and placement of the prosthetic disc during artificial disc replacement spine surgery. For templating, the critical parameters are height, width, depth and lordosis. For placement, there are different approaches of placing these artificial discs. Specifically, they can be placed anteriorly, laterally or posteriorly. The most common of these approaches is the anterior approach. A critical component of positioning of the prosthetic disc is the anterior-posterior position as this determines the center of rotation through the prosthesis and hence its dynamic function. If the prosthesis is placed anterior to the center of the disc space then the prosthesis will essentially function as a rigid device. Ideal placement of the prosthesis requires its instantaneous center of rotation to be in the posterior one-third of the disc space posterior to the center of the actual disc space. Templating of appropriate artificial disc implant size selection is often finalized at time of surgery. Subsequent placement of the prosthetic disc is aided by fluoroscopic or other image guidance.
To date many of the proprietary templating and placement systems and methods are manually determined by the surgeon at the time of surgery. As of yet, no apparatus or system is available which will automatically determine the ideal height, width, depth and lordosis or actual placement of an artificial intervertebral disc prosthesis.